Hablas espanol? Parlez-vous francais? 你会说中文吗？
你会说西班牙语吗？你会你讲法语吗？你会说中文吗？
If you answered, "si," "oui," and you're watching this in English,
如果你能回答 "si"，"oui"或是"会"，而且能用英文字幕观看这部短片，
chances are you belong to the world's bilingual and multilingual majority.
你就跟世界上大多数人一样，属于双语或多语的使用者。
And besides having an easier time traveling or watching movies without subtitles,
除了旅游时沟通比较方便，或是看电影时不需要字幕这些好处之外，
knowing two or more languages means that your brain may actually look and work differently than those of your monolingual friends.
通晓两种或三种以上的语言，表示你的脑袋在外表和运作方式上，与使用单一语言的朋友有明显的不同。
So what does it really mean to know a language?
究竟什么是通晓一种语言？
Language ability is typically measured in two active parts, speaking and writing, and two passive parts, listening and reading.
衡量语言的使用能力，包含两种主动能力：说、写；另外还有两种被动方式：听、阅读。
While a balanced bilingual has near equal abilities across the board in two languages,
虽然一个平衡的双语使用者，对于两种语言，具有相近的使用能力；
most bilinguals around the world know and use their languages in varying proportions.
但是大多数的双语使用者，当初如何学习并运用语言，有许多不同的方式。
And depending on their situation and how they acquired each language, they can be classified into three general types.
根据个人所处的环境，以及如何学习语言的方式，通常可以把双语使用者分为三类：
For example, let's take Gabriella, whose family immigrates to the US from Peru when she's two-years old.
举个例子来说，Gabriella在两岁时跟着家人由秘鲁移民到美国。
As a compound bilingual, Gabriella develops two linguistic codes simultaneously, with a single set of concepts,
作为一个复合型双语者，Gabriella在刚接触这个世界时就同时学英语和西班牙语，
learning both English and Spanish as she begins to process the world around her.
所以给她一个概念，她的大脑就能同时唤起两种语言信号。
Her teenage brother, on the other hand, might be a coordinate bilingual,
她有一个十几岁的弟弟，是属于对等型双语使用者，
working with two sets of concepts, learning English in school, while continuing to speak Spanish at home and with friends.
他运用两组不同的概念，一面在学校学习英语，一面用西班牙语，跟家人、朋友沟通。
Finally, Gabriella's parents are likely to be subordinate bilinguals
最后是加布瑞拉的父母，他们是从属型双语使用者。
who learn a secondary language by filtering it through their primary language.
当他们学习第二种语言时，需要透过母语进行翻译。
Because all types of bilingual people can become fully proficient in a language regardless of accent or pronunciation,
上述三种双语使用者，他们至少都能精通一种语言，无论是在腔调或是发音方面，
the difference may not be apparent to a casual observer.
因此，一般人难以发觉这三种类型的差异。

But recent advances in brain imaging technology have given neurolinguists a glimpse into how specific aspects of language learning affect the bilingual brain.
然而现在，由于大脑成像技术不断进步，神经语言学家得以窥探语言学习对于双语使用者的大脑产生何种影响。
It's well known that the brain's left hemisphere is more dominant and analytical in logical processes,
大家都知道，大脑的左半部主要掌管逻辑思考与分析，
while the right hemisphere is more active in emotional and social ones, though this is a matter of degree, not an absolute split.
而右半脑则掌管情感与社交活动，虽然左、右半脑有所区别，但并非完全独立运作。
The fact that language involves both types of functions while lateralization develops gradually with age,
事实上，语言同时包括了左脑与右脑的功能，而随着年纪增长，大脑功能逐渐侧重其中一边，
has lead to the critical period hypothesis.
这个观点发展出关键时期的假说。
According to this theory, children learn languages more easily
根据这个理论，儿童通常学习语言较快，
because the plasticity of their developing brains lets them use both hemispheres in language acquisition,
是因为大脑仍在发展，因此仍具有可塑性，他们可以同时利用左、右两边的大脑学习语言；
while in most adults, language is lateralized to one hemisphere, usually the left.
然而，多数成人会偏向採用其中一侧的大脑来学习语言，通常是左半脑。
If this is true, learning a language in childhood may give you a more holistic grasp of its social and emotional contexts.
如果这个观点正确，那么从小就学习语言，能够更容易掌握语言的社会和情感脉络。
Conversely, recent research showed that people who learned a second language in adulthood
相反地，最新的硏究指出：如果人们到了成年之后才学第二种语言，
exhibit less emotional bias and a more rational approach when confronting problems in the second language than in their native one.
当他们在使用第二种语言而非母语来处理问题时，会更理性，情绪化的偏见更少。
But regardless of when you acquire additional languages, being multilingual gives your brain some remarkable advantages.
不管你何时学习新的语言，多语言都能给你的大脑带来明显的好处。
Some of these are even visible, such as higher density of the grey matter that contains most of your brain's neurons and synapses,
有些好处，甚至可以看得见，例如大脑灰白质的密度增加，那里包含了脑部大多数的神经元和突触，
and more activity in certain regions when engaging a second language.
而且学习第二语言时，大脑部分区域会变得更活跃。
The heightened workout a bilingual brain receives throughout its life can also help delay the onset of diseases,
使用双语的大脑，持续不断地接受强化训练，能够让一些疾病的发作，
like Alzheimer's and dementia by as much as five years.
例如阿兹海默症与失智症，延迟高达五年之久。
The idea of major cognitive benefits to bilingualism may seem intuitive now, but it would have surprised earlier experts.
关于使用双语有助于人类认知的观点，在今天看似理所当然，但是对于从前的专家，他们必定会大吃一惊。
Before the 1960s, bilingualism was considered a handicap that slowed a child's development
在1960年代以前，人们认为使用双语对于儿童的发展是一种障碍，
by forcing them to spend too much energy distinguishing between languages, a view based largely on flawed studies.
因为需要迫使儿童花费精神去分辨两种语言，而这种观点主要来自于错误的研究。
And while a more recent study did show that reaction times and errors increase for some bilingual students in cross-language tests,
最新的硏究显示，在跨语言测验当中，使用双语学生的反应时间与错误次数增加了
it also showed that the effort and attention needed to switch between languages triggered more activity in,
这个结果显示，学生需要更努力与专注于转换语言，
and potentially strengthened, the dorsolateral prefrontal cortex.
这也使得前额叶脑区不仅更加活跃，而且能强化它的功能。
This is the part of the brain that plays a large role in executive function, problem solving,
前额叶脑区的主要工作，是进行决策、解决问题，
switching between tasks, and focusing while filtering out irrelevant information.
以及在多重任务中进行转换，还有集中注意力，同时排除无关的资讯。
So, while bilingualism may not necessarily make you smarter, it does make your brain more healthy, complex and actively engaged,
虽然学习双语，未必能让你更聪明，但是可以让大脑更加健康、多元以及活化。
and even if you didn't have the good fortune of learning a second language as a child,
即使在你年幼时，没有机会学习第二种语言，
it's never too late to do yourself a favor and make the linguistic leap from, "Hello," to "Hola"、"Bonjour"、"你好"
但是现在学习，永远不会太晚。学习外语的第一步，就是开始把"Hello"，转换为："Hola"、"Bonjour"或是 "你好"。
because when it comes to our brains a little exercise can go a long way.
只是小小的训练，就能对于大脑有所帮助。